1. Field of the Invention
This invention relates to a core shaft holding and gripping winding cores such as a paper tube for use in winding or unwinding of a sheet material, and more particularly, to an aligning core shaft that prevents runout of the winding cores and the resulting decentering.
2. Statement of Related Art
In winders for winding up a sheet material or unwinders thereof, hitherto a core shaft as shown in FIGS. 4 and 5 has been widely used, which is provided with lugs 24 interposing lug stays 23 and leaf springs 25 between a shell 21 of the core shaft and a rubber tube 22 in a manner that the lugs can protrude from the shell 21. The gripping of winding cores A by means of the core shaft is conducted so that when the rubber tube 22 is expanded by air admitted from an air inlet (not shown) into it, the lugs 24 are projected from the outer circumferential part of the shell 21 to come into press contact with the inner diameter of each winding core fitted externally on the core shaft, thus gripping the winding core.
With the conventional core shaft, the rubber tube 22 is located near a radially central part within the core shaft and the magnitude of protrusion of the lugs 24 is set with a sufficient margin to push up the inner surface of the winding core. Because of the construction, when the inside diameter of the shell 21 and the rubber tube 22 are expanded, a still protrudable clearance Sxe2x80x2 remains between the shell 21 and the lugs 24 retained within the inside core diameter, and the clearance cannot be kept constant. Consequently, the problem is encountered that the lugs 24 are freely movable by the amount of the clearance. The winding core A is therefore not only decentered, but also cannot be gripped concentrically with the core shaft since the winding core sags downwardly owing to the weights of the rubber tube 22 and the lugs 24.
Again, when the winding core A in that state is rotated at high speed, the winding core vibrates, so that the sheet-like material thereon cannot be wound stably and the resulting runout of the core causes a variation in the pass length of the sheet material during winding. The tension of the sheet material fluctuates, resulting in wrinkling of the wound product, accordingly.
On the other hand, another winding shaft device is disclosed in JP Patent First Publication No. 3-106744A (1991), which device is constructed so that grip members movable along inclination surfaces may be outthrusted by introduction of compressed air into a shaft body so as to grip winding tubes. Here, it is required that the device have both chuck mechanisms for gripping the winding tubes and clutch mechanisms for rotating the shaft body, and the clutch mechanisms be positioned inside the chuck mechanisms. Because of the construction, the iron core as the shaft body is inevitably so slender that the strength of the shaft is reduced and a deflection of the shaft is caused. Consequently, there is a defect of the difficulty in meeting a high-speed winding.
In particular, the recent requirement of a high productivity in winding of a film necessitates the winding of a wider film. To that end, the width of a film is enlarged to 2500 to 3000 mm against 1000 to 1500 mm in the past irrespective of the same core diameter of 75 mm as before and the winding speed is raised to 300 to 400 m/min.
Aside from the lugs of the known core shafts described above, another means for gripping winding cores concentrically are also known, namely, thread screws, a link mechanism, etc. However, these constructions are complicated and expensive since a number of components must be incorporated in a small space, considering the comparatively small diameter of the core.
In order to overcome the drawbacks or problems of the prior art core shafts, this invention is designed to provide an improved core shaft of the lug type as stated above. Accordingly, an essential object of the invention is to inhibit the movement of lugs within a shell of the core shaft, thereby securing concentrical gripping of winding cores with the core shaft and avoiding decentering and vibration of the winding cores, even upon high-speed winding of a wide film. Another object is ultimately to permit a smooth winding or unwinding of a sheet material.
The invention for attaining the aforesaid object resides generally in a core shaft of a required length which comprises, as its outer circumference, a plurality of sets of lugs arranged axially in spaced relationship and each protruding from the outer circumference to come into press contact with an inner surface of a winding core externally mounted, thus gripping the winding core. The core shaft is basically characterized in that at least one set of the lugs are disposed circumferentially equidistantly relative to the center of the core shaft; an inner core tube for the passage of air is disposed in a radially central part of the shaft; air cylinders having an inclined wall of a required angle are provided directly on an outer circumference of the inner core tube between the inner core tube and the lugs so that the inclined wall is axially movable; slide fittings having a reverse inclined wall to the inclined wall of the air cylinder are disposed in a manner that the reverse inclined wall is in facing contact with the inclined wall; and the slide fittings are fitted with the lugs so that when the inner core tube and the air cylinders are in communication with each other and air is moved through the cylinders, the inclined walls are moved to protrude the lugs equally or to retract the lugs from the outer circumferential surface of the shaft through the slide fittings.
More specifically, a first core shaft is characterized in that the slide fittings are fitted with the lugs so that when air is admitted into the inner core tube and the inner core tube communicates with the air cylinders, the inclined walls move to protrude the lugs equally from the outer circumference of the shaft through the slide fittings whereas when air is discharged, the inclined walls move in the opposite direction to retract the lugs from the outer circumference through the slide fittings.
In the foregoing core shaft of the construction that air is required to be always injected during winding, the requirement of perpetual injection of air necessitates the use of a number of air cylinders, which in turn requires a number of seal packings for the air cylinders. As a consequence, even if a leakage of air in a slight amount occurs, air pressure is lowered and the protruding force of the lugs is reduced, with the result that gripping force of securely gripping paper tubes or the like cannot be maintained. For that reason, it is also effective that the need for introduction of air during winding is dispensed with and air is introduced only when fitting or removing paper tubes or the like thereby to retract the lugs. That will do away with the need for an air injection device during winding and impede any reduction in the gripping force due to air leakage during winding. A second aspect of the invention is thus offered.
That is to say, a second winding core shaft is characterized in that at least one set of the lugs are disposed circumferentially equidistantly relative to the center of the core shaft on one circumference thereof; an inner core tube for passage of air is disposed in a radially central part of the shaft; air cylinders having an inclined wall of a required angle are provided directly on an outer circumference of the inner core tube between the inner core tube and the lugs so that the inclined wall is axially movable; slide fittings having a reverse inclined wall to the inclined wall of the air cylinder are disposed each in opposed contact with the air cylinder; the slide fittings are fitted with the lugs; and a spring member is fastened within each air cylinder with its one end attached to a spring retainer and its other end fixed to a cutout in the inclined wall of the air cylinder, thus forming an air chamber capable of admitting therein air between the spring retainer and a piston of the air cylinder; the air chamber being constructed so that during winding, the air chamber is in an evacuated state and the inclined wall of the cylinder is moved in one direction by the biasing force of the spring member to protrude the lugs equally from the outer circumference of the shaft through the slide fittings whereas when winding cores are fitted or removed, the inner core tube and the air chamber are put into communication with each other and air is admitted in the air chamber, while the spring member is compressed to move the inclined wall of the cylinder in the opposite direction thereby to retract the lugs through the slide fittings.
In accordance with the first core shaft relating to the present invention, when winding cores such as a paper tube are inserted thereon, air is supplied from an air port through the inner core tube into the air cylinders, the inclined walls move, and then the slide fittings in opposed contact with the inclined walls are outthrusted circumferentially outwardly. The lugs fitted to the slide fittings thus protrude from the outer circumference of the shaft so as to bring them into contact with the inner surfaces of the winding cores.
At that time, since the lugs are arranged circumferentially equidistantly relative to the center of the winding core, an equal protrusion of the lugs is possible and an alignment of the core shaft is achieved. On the other hand, when air in the air cylinders is evacuated, the inclined walls thereof are displaced circumferentially inwardly by means of a coil spring (not shown) to be restored and the lugs are retracted. The winding cores are thus released easily from the core shaft.
With the second winding core shaft, upon mounting of the winding cores, when air is introduced from an air port through the inner core tube into the air chambers in the air cylinders, the spring members are compressed and the pistons are displaced to move the inclined walls of the cylinders. Concurrently, the slide fittings in facing contact therewith are displaced circumferentially inwardly and the lugs fitted to the slide fittings are retracted from the outer circumference. Accordingly, the mounting operation of the winding cores is easily performed.
In conducting winding process after the mounting of the winding cores, air is evacuated from the air chambers and the biasing force of the spring members is restored. Then the pistons within the cylinders are slidingly moved to the position of the spring retainers. At that time, the inclined walls of the cylinders and the slide fittings in abutting contact therewith are moved circumferentially outwardly to protrude the lugs from the outer circumference so as to bring the lugs into press contact with the inner surfaces of the winding cores thereby gripping them.
Now during winding, air is not introduced and the lugs protrude through the slide fittings while sustaining the inclined walls of the cylinders only by the force of the spring members. Consequently, air leakage never occurs during winding.
After the winding process is finished, in removing the winding cores, air is admitted, as is the case with the mounting thereof. At that time, the pistons of the cylinders are moved to slide by the air pressure and the spring members are compressed by means of the spring retainers to move the inclined walls of the cylinders. Thereby the lugs are retracted through the slide fittings whereby the removal of the winding cores is conducted.
During the aforesaid winding process, since the lugs are arranged to be equal to one another on one circumference relative to the center of the winding cores, an even, equal protrusion of the lugs is possible and alignment of the shaft is attained, accordingly.